Arylthioureidoisoindolines and use as plant growth regulators

ABSTRACT

A novel class of compounds which are useful as plant growth regulators has the general structural formula   &lt;IMAGE&gt;   in which R is H or CH3, R&#39; is halogen, trifluoromethyl, cyano or C1 to C3 alkyl or alkoxy and n is zero or an integer from 1 to 2. The compounds are synthesized by reacting a compound of the formula   &lt;IMAGE&gt;  with an isocyanate of the formula   &lt;IMAGE&gt;  under basic conditions in a non-reactive, polar organic solvent.

DESCRIPTION OF THE INVENTION

I have discovered a novel class of compounds which are useful as growth regulators, particularly for the purpose of yield enhancement or increasing the fruit set of crop plants. The novel compounds have the general structural formula ##STR4## in which R is H or CH₃, R' is halogen, trifluoromethyl, cyano or C₁ to C₃ alkyl or alkoxy and n is zero or an integer from 1 to 2. This invention is also directed to a method of synthesis of the novel class of compounds and use of the compounds to regulate growth of plants.

SYNTHESIS OF THE GROWTH REGULATORS

The novel growth regulator compounds of this invention may be made by means of the general reaction outlined below: ##STR5## in which HX represents hydrochloric or other strong acid. The organic base, which serves as an acid acceptor, is preferably a strongly basic organic amino compound, such as triethylamine. Specific procedures are outlined and exemplified below for illustrative purposes: ##STR6##

The N-amino dihydroisoindole hydrochloride is prepared as taught by L. A. Carpino, J.A.C.S., 79, 4427(1957). The t-butyl 2-methyl-carbazate is prepared as taught by A. S. Dutta and J. S. Morley, J.C.S. Perkin I, 1712(1975). Below are specific, illustrative procedures.

Preparation of N-(phenylthioureido)-dihydroisoindole

To a solution of 1.7 g (0.01 mole) of N-amino dihydroisoindole hydrochloride in 10 ml of dimethyl formamide was added 1 ml of triethylamine followed by 1.35 g (0.01 mole) of phenylisothiocyanate. The reaction mixture was allowed to stir at room temperature overnight. Water (25 ml) was added, the mixture stirred for 1 hr., and filtered. After drying there was obtained 2.6 g of the desired product, mp: 192°-193° dec. The IR and NMR were consistent with the proposed structure.

Preparation of N-(t-butyloxy carbonyl-methylamino)dihydroisoindole

A vigorously stirred solution 13.15 g (0.05 mole) of o-xylylene dibromide and 7.3 g (0.05 mole) of t-butyl 2-methylcarbazate in 25 ml of dimethylformamide was warmed to 50° and 14 ml of triethylamine was added during 5-8 minutes while maintaining the temperature at 50°-60°. After complete addition the reaction mixture was stirred at room temperature for 3 hrs. and diluted with 100 ml of water. After stirring for 1 hr the mixture was extracted with ethyl acetate. The organic phase was separated and dried. Filtration and evaporation gave a gummy solid which was used without further purification. The IR and NMR of the material were consistent with the proposed structure.

Preparation of N-methylaminodihydroisoindole hydrochloride

To the crude N-(t-butyloxycarbonyl-N-methylamino)dihydroisoindole from the above preparation was added 25 ml of concentrated hydrochloric acid. The reaction mixture was allowed to stir for one hour. Evaporation of the mixture to dryness and recrystallization of the residue from ethanol-ether gave 5.6 g of the desired product as a gummy solid, mp: 79°-89°. The IR and NMR were consistent with the proposed structure.

Preparation of N-(1-methyl-3-phenyl thioureido)dihydroisoindole

To a solution of 1.12 g (0.006 mole) of N-methylamino dihydroisoindole hydrochloride in 10 ml of dimethylformamide was added 1 ml of triethylamine followed by 0.82 g (0.006 mole) of phenylisothiocyanate. The reaction mixture was allowed to stir at room temperature overnight. Water (25 ml) was added and the resulting gummy solid was extracted with ethyl acetate. After drying and filtering, evaporation gave a thick oil which solidified upon adding a small amount of ether and scratching. There was obtained 1.4 g of the desired product, mp: 121°-125° dec. The IR and NMR were consistent with the proposed structure.

Compounds of the invention which have been made by methods illustrated above are disclosed in Table I.

                  TABLE I                                                          ______________________________________                                         COMPOUNDS OF THE FORMULA                                                        ##STR7##                                                                      M-No       m.p. °C.                                                                            R         (R')n                                         ______________________________________                                         3987       192-3°                                                                              H         H                                             4053       183-4       H         3-CH.sub.3                                    4054       177-9       H         3-Cl                                          4055       184-6       H         4-F                                           4056       176-9       H         2-F                                           4057       177-180     H         4-CF.sub.3                                    4249       121-5       CH.sub.3  H                                             4250       134-142     CH.sub.3  4-Cl                                          4251       104-113     CH.sub.3  3-Cl                                          4252       149-156     CH.sub.3  4-F                                           4253       128-138     CH.sub.3  3-F                                           4322       208-210     H         3-CN                                          4323       174-177     H         3-F                                           4324        87-102     H         4-Cl                                          4325       185-188     H         4-CH.sub.3                                    4326       171-176     H         2,4-Cl.sub.2                                  4327       166-172     H         3,4-Cl.sub.2                                  4424       192-193     H         2-Cl                                          4425       171-174     H         2,3-Cl.sub.2                                  4426       183-187     H         4-OCH.sub.3                                   4427       198-199     H         2-CH.sub.3                                    4428       174-177     H         3,4-(CH.sub.3).sub.2                          ______________________________________                                    

Use of the Growth Regulators

The effects of these compounds as growth regulators, resulting from both pre-emergent and post-emergent application are often readily apparent. These effects may be demonstrated by means of the following illustrative procedures.

Pre-emergent Application

Disposable paper trays about 21/2 inches deep were filled with soil and sprayed with aqueous spray mixtures at at rate of 5 lb. of active chemical per acre of sprayed area, were seeded with 6 species of plant seeds and were then covered with about 1/4 inch of soil. The spray mixtures were prepared by dissolving the proper amount of growth regulator compound in 15 ml of acetone, adding 4 ml of a solvent-emulsifier mixture consisting of 60 wt. percent of a commercial polyoxyethylated vegetable oil emulsifier (96 wt. percent active ingredient, Emulphor EL-719), 20 wt. percent xylene and 20 wt. percent deodorized kerosene, then bringing total volume up to 60 ml by addition of warm water. Twenty-one days after seeding and treatment the plantings were examined and plant injury was rated according to the following schedule:

DEGREE OF EFFECT

0=no effect

1=slight effect, plants recovered

2=moderate effect, injury to 26 to 75 percent

3=severe effect, injury to 76 to 93 percent of foliage

4=maximum effect (all plants died)

Post-emergent Application

Several species of plants were grown in potting soil in disposable expanded cellular polystyrene trays and tomatoes were grown in four-inch pots in the greenhouse. Aqueous spray formulations were prepared and the growing plants were sprayed at a spray volume of 60 gallons per acre and an application rate of 5 lb. per acre. Spray mixtures were prepared in the manner described above. For comparative purposes, plants were also sprayed at 60 gal./acre with a spray mixture containing no growth regulator. Plant injury was again rated according to the schedule disclosed above and observations of growth regulator effects were observed and recorded as follows, for both pre- and post-emergent applications:

    ______________________________________                                         Effect              Abbreviation in Tables                                     ______________________________________                                         Formative effect on new growth                                                                     F                                                          Epinasty            E                                                          Growth reduction    G                                                          Non-emergence       K                                                          Necrosis            N                                                          ______________________________________                                    

In Table II below there are tabulated the observations of pre- and post-emergent herbicidal and growth regulator effects of various compounds disclosed above.

                                      TABLE II                                     __________________________________________________________________________     EFFECTS ON VEGETATION                                                          Pre-emergent Effects        Post-emergent Effects                                  Digit-                                                                     Com-                                                                               aria             Raph-                                                                              Beta   Medi-   Raph-                                                                              Beta                               pound                                                                              sangui-                                                                            Celosia                                                                             Bromus                                                                             Setaria                                                                            anus                                                                               vul-                                                                              Setaria                                                                            cago                                                                               Avena                                                                              anus                                                                               vul-                                                                              Lycopersicum                    No. nalis                                                                              plumosa                                                                             inermis                                                                            italica                                                                            satiuus                                                                            garis                                                                             italica                                                                            sativa                                                                             sativa                                                                             sativus                                                                            garis                                                                             esculentum                                                                            Comments                 __________________________________________________________________________     3987                                                                               0   0    F1  0   0   0  0   F2G1                                                                               0   0   F2G2                                                                              F2                              4053                                                                               0   F1   F1  F1  0   F2G1                                                                              F1  F3G1                                                                               F1  F1  F3G1                                                                              F1     Increased fruit                                                                set                      4055                                                                               0   0    F2G1                                                                               0   0   F1 F1  F3G3                                                                               F1  F1  F3G3                                                                              F1     Increased                                                                      tillering                4056                                                                               0   F1   F2  0   0   F2G1                                                                              F1  F3G3                                                                               F1  0   F3G3                                                                              F1     Increased                                                                      tillering                4057                                                                               0   F1   F1  0   0   F1 0   F3G1                                                                               0   F1  F2 0                               4249                                                                               0   0    0   0   0   0  F1  F2G1                                                                               --  F1  F1G1                                                                              F1                              4250                                                                               0   0    0   0   0   0  F1  F1  0   0   F1 0                               4251                                                                               0   0    0   0   0   0  F2G1                                                                               F1  F1  F1  F3G1                                                                              F2     Increased fruit                                                                set                      4252                                                                               0   0    0   0   0   0  0   0   0   0   F1 0                               4253                                                                               0   0    0   0   0   0  F1  F2  F1  F2G1                                                                               F2G1                                                                              F2     Increased fruit                                                                set                      4322                                                                               0   0    0   0   0   0  N1  F1  0   0   F1 F1                              4323                                                                               F2G1                                                                               F2G2 F2G1                                                                               F2G1                                                                               0   F1G1                                                                              F1  F3G2                                                                               F1  F1  F3G1                                                                              F2                              4324                                                                               0   0    0   0   0   0  0   F2G1                                                                               0   F1  F2 F1                              4325                                                                               0   0    F1G1                                                                               F1G1                                                                               0   F1 0   F2G1                                                                               F1  0   F2 F1                              4326                                                                               0   0    0   0   0   F1 F1  F2G1                                                                               F1  F1  F2 F2                              4327                                                                               F3G2                                                                               F2G1 F3G1                                                                               F3G3                                                                               0   F1 0   F3G1                                                                               0   0   F1 F1     Increased fruit                                                                set                      4424                                                                               0   0    0   0   0   0  N1  F1  0   0   F1 0                               4426                                                                               0   0    0   0   0   0  0   F1  0   0   F1 F1                              4427                                                                               0   0    0   0   0   0  0   0   0   0   F1 F1                              4428                                                                               0   0    0   0   0   0  0   F1  0   0   F1 F1                              __________________________________________________________________________

The use of many of the growth regulator compounds may be demonstrated by treatment of soybeans (Soja max) to increase the number of seed pods and by treating tomato plants (Lycopersicum esculentum) to increase fruit set. In an illustrative experiment, Soja max (Evans variety) and Lycopersicum esculentum (Tiny Tim variety) were grown in 4-inch pots (one plant per pot) filled with greenhouse potting soil (2 parts good top soil, 11/2 parts builders' sand, 11/2 parts peat, fertilized with 5 lb. of 12-12-6 fertilizer and 5 lb. of finely ground limestone per cu. yd.). Aqueous spray formulations were prepared and the potted plants were sprayed at a spray volume of 40 gal. per acre and at application rates of 16, 4, 1 and 1/4 oz. per acre. The spray mixtures were prepared by dissolving the proper amount of growth regulator compound in 15 ml. of acetone, adding 2 ml. of a solvent-emulsifier mixture consisting of 60 wt. percent of a commercial polyoxyethylated vegetable oil emulsifier (96 wt. percent active ingredient, Emulphor EL-719), 20 wt. percent xylene and 20 wt. percent deodorized kerosene, then bringing total volume up to 80 ml by addition of a 0.156 wt. percent aqueous solution of liquid non-ionic dispersant (90 wt. percent active trimethylnonyl polyethylene glycol ether, Tergitol TMN-10). Two replicates were sprayed at all application rates. For comparative purposes, plants were also sprayed at 40 gal./acre with water. The number of seed pods and of fruits on both treated and on untreated plants was observed within approximately three weeks after spray treatment and the results are tabulated below as averages of two replicates. The fruit set is expressed as percentage of average pod or fruit count on treated plants, in comparison with average count on untreated plants. The severity of growth regulatory effect on the plants was estimated on a scale of 0 to 10 and is also recorded in the following table:

                  TABLE III                                                        ______________________________________                                         GROWTH REGULATING EFFECTS ON TWO SPECIES                                               Lycopersicum esculentum                                                                      Soja max                                                                                        Pod Count                                             Sever-            Sever- Percent                                               ity of   Fruit Count                                                                             ity of in Com-                                               Growth   Percent in                                                                              Growth parison                                               Regu-    Comparison                                                                              Regu-  to Un-                                  Comp'd.                                                                               Rate   lating   to Untreated                                                                            lating treated                                 No.    oz/A   Effect   Plants   Effect Plants                                  ______________________________________                                         3987   16     0        100      3.5    123                                            4      0        50       0.5    98                                             1      0        0        0      94                                      4053   16     1.5      400      1.5    101                                            4      0        200      1      91                                             1      0        300      0      101                                     4054   16     0        200      0.5    105                                            4      0        600      0      105                                            1      0        100      0      94                                      4055   16     0.5      300      1.5    153                                            4      0        100      0      115                                            1      0        0        0      87                                      4056   16     0.5      400      2.5    112                                            4      0.5      300      0.5    129                                            1      0        100      0      80                                      4057   16     0        100      1.5    167                                            4      0        200      1      122                                            1      0        100      0      129                                     4249   16     0        150      3.5    93                                             4      0        175      0.5    105                                            1      0        150      0      89                                      4250   16     0        113      0      93                                             4      0        125      0      105                                            1      0        113      0      114                                     4251   16     1        175      0.5    73                                             4      0        113      0      93                                             1      0        100      0      93                                      4252   16     0        113      1.5    89                                             4      0        113      0      109                                            1      0        100      0      81                                      4253   16     1.5      113      1      97                                             4      0.5      88       0      89                                             1      0        113      0      93                                      4310   16     0        87       0      96                                             4      0        106      0      118                                            1      0        144      0      96                                      4322   16     0        136      0      114                                            4      0        150      0      91                                             1      0        95       0      105                                     4326   16     0.5      177      1      118                                            4      0        150      0      118                                            1      0        150      0      105                                     ______________________________________                                    

The information presented in tabular form herein will enable a worker in the art to make a selection from among the growth regulator compounds of the invention and to make some judgment with regard to application rates, depending upon the effect which is desired. It may be seen, for example, that severe effects on some species of vegetation may occur at application rates of only 5 lb. per acre, whereas beneficial effects may be observed on living plants at application rates of 1 lb. per acre or less.

The growth regulator compounds are usually applied in combination with inert carriers or diluents, as in aqueous sprays, granules and dust formulations in accordance with established practice in the art. An aqueous spray is usually prepared by mixing a wettable powder or emulsifiable formulation of a growth regulator with a relatively large amount of water to form a dispersion.

Wettable powders comprise intimate, finely divided mixtures of growth regulator compounds, inert solid carriers and surface active agents. The inert solid carrier is usually chosen from among the attapulgite clays, the kaolin clays, the montmorillonite clays, the diatomaceous earths, finely divided silica and purified silicates. Effective surfactants, which have wetting, penetrating and dispersing ability are usually present in a wettable powder formulation in proportions of from 0.5 to about 10 percent by weight. Among the surface active agents commonly used for this purpose are the sulfonated lignins, naphthalenesulfonates and condensed naphthalenesulfonates, alkylbenzenesulfonates, alkyl sulfates and non-ionic surfactants such as products of condensation of ethylene oxide with alkylphenols.

Emulsifiable concentrates of the growth regulator compounds comprise in each instance, a solution of growth regulator compound in a liquid carrier which is a mixture of water-immiscible solvent and surfactants, including emulsifiers. Useful solvents include aromatic hydrocarbon solvents such as the xylenes, alkylnaphthalenes, petroleum distillates, terpene solvents, ether-alcohols and organic ester solvents. Suitable emulsifiers, dispersing and wetting agents may be selected from the same classes of products which are employed in formulating wettable powders.

Usually, the growth regulators are applied by diluting with water agricultural compositions which desirably contain from 0.1 percent to 95 percent by weight of active compound and from 0.1 to 75 percent of a carrier or surfactant. However, direct application to plant seeds prior to planting may be accomplished in some instances by mixing powdered solid growth regulator with seed to obtain a substantially uniform coating which is very thin and comprises only one or two percent by weight or less, based on the weight of the seed. In most instances, however, a nonphytotoxic solvent, such as methanol is employed as a carrier to facilitate the uniform distribution of growth regulator on the surface of the seed.

When a compound is to be applied to the soil, as for a pre-emergence application, granular formulations are sometimes more convenient than sprays. A typical granular formulation comprises the growth regulator compound dispersed on an inert carrier such as coarsely ground clay, or clay which has been converted to granules by treatment of a rolling bed of the powdered material with a small amount of liquid in a granulating drum. In the usual process for preparing granular formulations, a solution of the active compound is sprayed on the granules while they are being agitated in a suitable mixing apparatus, after which the granules are dried with a current of air during continued agitation. 

I claim:
 1. The method of regulating the growth of plants which comprises applying to the plants pre- or post- emergently an effective amount of a composition comprising from 0.1 percent to 95 weight percent of a compound having the structural formula ##STR8## in which R is H or CH₃, R' is halogen, trifluoromethyl, cyano or C₁ to C₃ alkyl or C₁ to C₃ alkoxy and n is zero or an integer from 1 to 2, in combination with from 0.1 to 75 weight percent of a carrier or surfactant.
 2. The method of increasing fruit set of crop plants which comprises applying to the plant foliage an effective amount of a compound having the structural formula ##STR9## in which R is H or CH₃, R' is halogen, trifluoromethyl, cyano or C₁ to C₃ alkyl or C₁ or C₃ alkoxy and n is zero or an integer from 1 to 2, in combination with an inert carrier and a surfactant.
 3. The method of claim 2 in which the crop plants are of the species Lycopersicum esculentum.
 4. The method of claim 2 in which the crop plants are of the species Soja max. 